Floor coverings such as rugs or carpets often consist of dyed pile yarns, a primary support material (also called “backing”), and in many cases a secondary backing that adds strength to the carpet. The yarns are usually contacted with the primary support material by a process called tufting, which is a type of textile weaving in which a thread is attached to the support material by mere insertion in that material. Such tufting does not provide adequate mechanical bonding between the yarns and the support material. Usually an adhesive is used to provide adequate mechanical bonding between the yarns and the primary and, if present, the secondary backings.
Ninety-seven percent of pile yarns today are made up of synthetic polymers. Synthetic polymers are for example nylon (which is in 66% of all carpet), acrylics (15%), polyester (less than 15%), polypropylene (less than 5%) and blends thereof. These pile yarns are dyed using a variety of organic chemical compounds, or occasionally, organometallic complexes. The backing is in most cases made of woven or non woven polypropylene. The adhesive used to bind the backings together is almost universally synthetic rubber latex.
Latex based floor coverings have several disadvantages. Firstly, since the latex is water-based, latex coverings tend to be non-resistant to moisture. They may allow moisture to pass through which on its turn can lead to the formation of mildew and molds. This cannot only degrade the floor covering, but may also lead to environmental hazards such as poor air quality. As a consequence, when latex based floor coverings are placed in an area where moisture is a concern, for example in lobbies, they may need to be frequently replaced. Secondly, because latex-based floor coverings use dissimilar materials for the yarns, the backing and the adhesive, such coverings cannot be fully recycled. Carpet recycling technologies have been developed but are expensive and do not allow complete recycling of the materials used, mainly due to the intense embedding of the yarns and backing in the vulcanized latex. As a result, most floor coverings are simply discarded, burned or shredded. At best, shredded floor coverings are used as landfills but since vulcanized latex is hardly biodegradable, the shredded remains will be present for many years.
In the art, several solutions have been proposed to overcome or at least mitigate the above described disadvantages. One solution is to replace the conventional latex adhesive with synthetic polymer adhesives such as polyolefines and polyurethanes. This is for example known from US 2010/0260966, which discloses a carpet tile that includes a face fabric having a top surface and a base, and a dimensionally stabilized non-woven cushion material having a stabilizing material incorporated therein. The non-woven cushion material is attached to the face fabric by using a synthetic polymer adhesive, in which adhesive the cushion material as well as the fabric are embedded for adequate bonding. Still, complete recycling of this known carpet tile is hardly possible due to the embedding of the face fabric and the cushion material in the polymer. At best, when worn, these carpets are shaven to release a (small) part of the pile yarns for recycling.
Another solution proposed is the use of hot melt adhesives. These adhesives are popular in conventional roll carpets since they are relatively inexpensive, readily available and can be recycled more easily. Hot melt adhesives are also used in carpet tiles, as is known for example from WO 2007/127222. Still, given the fact that the bonding of the face fabric with the backing when using a hot melt adhesive needs substantial embedding of the materials in this adhesive, complete recycling remains hard. Either the face fabric, the backing or both will inevitably be contaminated with substantial amounts of the adhesive.
Also, floor coverings based on biodegradable materials are commercially available. These floor coverings, mainly carpets, carpet tiles and rugs are in most cases based on a pile of yarns comprising keratin fibres (mainly wool), and a backing based on material comprising cellulose fibres such as jute. These floor coverings can be obtained for example from InterfaceFlor, Scherpenzeel and Desso, Waalwijk, both in The Netherlands. The fact that these floor coverings largely comprise materials of natural origin, which materials are additionally biodegradable, makes these carpets far more environmentally friendly. They can at least partly be recycled and the corresponding carbon dioxide emission is substantially less when compared to fully synthetic floor coverings. However, the adhesive used to bond the yarns to the backing, in most cases still latex, is not biodegradable.